Radio control system for moving vehicles



D. S.' KELLOG G CONTROL SYSTEM FOR MOVING VEHICLES 4 Sheets-Sheet 1 April 2, 1946.

RADIO Filed March 25, 1940 i wmmse INVENTOR. DONALD S. KELLOGG BYZ ATTORNEYS April 1946. D. s. KELLOGG 2,397,477

RADIO CONTROL SYSTEM FOR MOVING VEHICLES Filed March 23, 1940 4 Sheets-Sheet 2 DONALD S. KELLOGG BY 441 M ATTORNEYS,

INVENTOR. Y

April 2, 1946. D. s. KELLOGG RADIO CONTROL SYSTEM FOR MOVING VEHICLES 4 Sheets-Sheet 5 Filed March 25, 1940 INVENTOR.

DONALD s. KELLOGG skl L ATTORNEYJ April 1946- D. s. KELLOGG 2,397,477

RADIO CONTROL SYSTEM FOR MOVING VEHICLES Filed March 23, 1940 4 Sheets-Sheet 4 INVENTOR. DONALD S. KELLOGG ATTORNEYS.

Patented Apr. 2, 1946 UNITED STATES PATENT OFFICE RADIO CONTROL SYSTEM FOR MOVING VEHICLES Application March 23, 1940, Serial No. 325,497

" 11 Claims.

This invention relates to the control of one or more parts of a device from a remote point by means of electrical impulses, and more especially to the control of certain parts of an airplane, ship or other movable vehicle or to a part or parts of an object carried by the vehicle. As illustrations of the use to which the invention is adapted, it may be employed to control the elevators, ailerons, rudder and other movable parts of an airplane which control its flight. The invention is also adapted to control instruments or objects carried by the plane such as radio receivers or transmitters, cameras, etc., or to control devices adapted to release objects such as bombs, etc.. from airplanes.

In pursuance of the invention, the control is effected by radio signals and preferably by transmission to the vehicle of a carrier wave of radio frequency, a suitable radio receiver being provided on the vehicle to receive the control signals and transmit them to suitable apparatus which accomplishes the desired control of the intended part or parts.

It is an object of the invention to effect the control of the desired part or parts in any direction and through any desired extent or angle of adjustment by the transmission of pulses of energy of controlled duration and to provide, at the controlled device, suitable mechanism which effects the control in accordance with the duration of the pulses.

To provide energy pulses of a duration closely corresponding to the extent of adjustment of the control member, it is a further object of the invention to provide at the transmitting station a novel means and method for controlling the action of one or more oscillators which effect the modulation of the transmitted canier wave. In pursuance of this object, the control of the os cillators is preferably effected by a novel circuit arrangement which includes a relay and a relay control device comprising a Wheatstone bridge arrangement.

In accordance with a further object of the invention, the control of the movable controlled part on the airplane or other vehicle is eiiected by a control handle located at a ground station or in another vehicle, the controlled member moving in one direction or in an opposite direction in accordance with the movement of the control handle in one direction or in an opposite direction from a neutral position thereof. The control handle or stick is preferably mounted for universal movement similar to the control stick of an airplane, so that it may be mounted to rotate either of two shafts disposed at right-angles to each other or to rotate both shafts together to effect the control of two diflerent controlled members simultaneously. I

A still further object of the invention is to provide a control arrangement which includes a Wheatstone bridge so arranged as to cause the controlled member to be operated substantially in synchronism with the control stick. This object is effected by means which includes one or more compensating resistors which are so associated with the bridge circuit as to secure uniform sensitivity throughout the contro1 range.

Another object of the invention is to provide in association with a galvanometer relay disposed across the neutral points of a Wheatstone bridge, a resistor arrangement for controlling the sensitivity level. This resistor arrangement is preferably so arranged that the impedance of the gal= vanometer leg of the circuit remains substantially constant for difierent sensitivity levels as established 'by different resistor settings.

Other and further objects of the invention will become apparent to those skilled in the art as the description thereof proceeds. For a better understanding of the invention, however, reference is made to the accompanying drawings in which:

Fig. 1 is a schematic circuit diagram of a radio transmission system embodying the invention and also showing certain mechanical control features schematically; v

Fig. 2 is an extension of the transmission system of Fig. 1 showing another unit thereof;

Fig. 3 is a schematic circuit diagram of a radio receiving system embodying the invention and also showing a unit of the controlled apparatus schematically; and

Fig. 4 is an extension of the receiving system of Fig. 3 showing a second unit of the controlled 7 apparatus.

Referring to Fig. 1, a rotatable control shaft l is shown as provided with a control lever or stick 2 mounted for universal movement, in the manher of the usual control stick of an airplane, so that its rotation in a plane normal to the longitudinal axis of shaft I causes rotation of this shaft while its rotation in a plane passing through the axis of shaft l causes rotation of a second shaft 3 mounted to rotate about a lateral axis at right-angles to shaft I. Rotation of lever 2 in intermediate planes obviously causes rotation of both the shafts l and 3 simultaneously. In the illustrated embodiment of the invention, the

lower end of the lever 2 is provided with an en-- a accuser to unbalance a Wheatstone bridge circuit which directly connected to one end or a resistor and comprises abattery whose positive terminal is whose negative terminal is connected to the opposlte end of resistor Q'through the rheostat arm ill secured to shaft i3 and movable along a compensating resistor ii, the midpoint of resistor it being connected to the end of resistor ii through the lead shown. The resistor 9 forms two arms or the Wheatstone bridge, the other two opposite arms being formed by a resistor 02 whose ends are connected, as shown, to the opposite ends of resistor ii. The cross arm of the bridge circuit, or the circuit which connects the conjugate neutral points of the bridge when it is balanced, cornprises arheostat arm [13 secured to the shaft is and adjustable along resistor 9, a series resistor 93, a variable resistor M which is connected in shunt across the coil windings lb of a polarized or galvanometer relay it, and a rheostat arm ll which is adjustable along the resistor 02 andsecured to a shaft 88.;

With the stick 2 in its neutral position, as indicated at N, the rheostat arm 83 is at the center of resistor 9 and rheostat arm ill at the center of resistor i2 and the bridge is balanced, with no current passing through the relay winding ill so that the relay armature it is centrally disposed between its upper and lower contacts iii and 20. Movement of stick 2 rearwardly in the direction it into the full line position shown, causes rheostat arm it to be moved from. the center or resistor ii into the full line position shown. thereby changthat the output of transmitter 35 is normally modulated by the tone frequencies of both the generators 22 and and that the tone frequency of generator 22, for example, is caused to be climinated from transmission by movement of the stick 2 rearwardly in the direction it from its neutral position and the tone frequency of gem erator 23 eliminated from the transmission by movement of the stick forwardly in the direction Assuming that movement or the sticlr. 2 rearwardly and the consequent 'unbalancing of the bridge circuit causes the relay armature it to engage the lower contact 2f], the closure of this contact causes the operation of a relay til whose coil is connected across the positive and negative terminals of battery ii through the armature I19, lower relay contact 20 and the circuit shown. Operation of relay ill causes its upper and lower contacts 38 and 39 to close, the closure of contact 38 causing a short-circuiting of resistor 26 a through the circuit connections shown with the consequent elimination of the tone frequency of generator 22 from the transmission. The elimination of this tone frequency continues during the interval of time elapslng until the bridge circuit is again balanced.

The preferred means for automatically balancing the bridge circuit comprises a differential gearing device 80 having the output shaft 9 8 and a pair of input shafts M and #32 adapted to be rotated in opposite directions by the impulse motors 43 and 44. Each of these motors comprises. a magnet d5 having an armature 6 pivoted at 6'5 and carrying a pawl 58 adapted to rotate a ratchet wheel 39. the ratchet wheels 89 being mounted on the difierential input shafts 6i and 42.

Passage of current through relay magnet of motor 33 causes its armature (iii to be rotated in a counter=clockwise direction, causing the pawl 48 to be moved to the right a distance sum'cient to engage it behind the next ratchet ing its potential with reference to the rheostat arm Ill and unbalancing the bridge circuit, the

amount or degree or this unbalance depending on the extent of rotation of stick 2 and shaft The effect of unbalancing the bridge circuit is to eliminate the tone frequency of one of two audio frequency generators 22, 23 from the transmission as long as the bridge circuit remains unbalanced. Each of these generators comprises a vacuum tube oscillator, such as 226, whos output terminals are connected through the'resist ance networks 25, 2t, 2?, 28, Eli, 3b and transformer 3i to. the tone bus bars the resistors 25, fit, etc., preferably being adjustable, as indicated. The generators 22, 23am preferably olesigned to generate tone frequencies of i020 and 1380 cycles per second, respectively, although it will be understood that any other suitable fr quencies may be used. The tone bus bars are connected by any suitable means, such as the transformer 33 and variable resistor 36 to the modulator input terminals of a radio frequency transmitter 35 arranged to generate a carrier current of constant frequency. The output terminals of transmitter 35 are connected to an antenna When the transmitting equipment is located at a ground station, one of the transmitter terminals may be connected to ground, as shown, and when the transmitting equipment is mounted on a movable vehicle, as for example, in another airplane, any suitable lmown type of transmitting antenna may be provided. it will be understood tooth. The motor circuit is simultaneously broken by a movable contact 50 which is opened by the movement of the armature d6, whereupon a spring 56 connected to armature 68 causes the pawl "38 to advance the ratchet wheel $9 a distance of one tooth in a counter-clockwise direction. A suitable holding pawl Ella is provided to engage the ratchet wheel as to prevent retrograde movement thereof. This operation is repeated causing the rotation of diflerential 60 and shaft l8 until the rheostat arm l'i has been rotated along resistor l2 through a suflicient angle as to again balance the bridge circuit. The closure of the lower relay contact 39 completes a circuit including the lead 5?, battery 8, coil of magnet 45, movable contact 56 and the leads shown, thereby causing the operationof motor (S3 in the manner above described. Upon the rheostat arm ill being adjusted by the motor 83 into such a position on the resistor l2 as to balance the bridge circuit, current will cease to flow through the winding lb of the polarized relay it so that its armature it] returns to its normal central position, as shown, thereby breaking the circuit through the relay 3 and causing the opening of its upper and lower relay contacts 38 and 353. Opening of the contact 39 breaks the circuit of the energizing winding '35 of motor (43 and stops the motor. The opening of contact 33 discontinues the short=clrcuit of resistor 25, and thereby restores the tone frequency oi'generator 22 to the Upon movement of the stick 2 forwardly in the direction F, movement of the rheostat arm l3 along resistor 9 imbalances the bridge circuit in such a direction as to cause the relay armature l9 to close the upper relay contact 20 which in turn causes the relay 53 to be energized by current from battery 8 through the circuit connections shown including the upper contact 20 and armature l9. Operation of relay 53 causes its contacts 54 and 55 to close, the closure of contact 54 causing a short-circuiting of resistor 29 through the circuit shown with the consequent elimination of the tone frequency of generator 23 from transmission. The elimination of this tone frequency continues until the bridge circuit is again brought to a balance. This balancing is initiated by the closure of the lower relay contact 55 which completes the circuit shown, including the contact 55, lead 52, battery 8, magnet coil 45 of impulse motor 44, and movable contact 50, thereby causing the operation of motor 44 and the rotation of rheostat arm I! along resistor I2 in a clockwise direction a distance sufficient to rebalance the bridge circuit. Current then ceases to flow through the winding [5 of the polarized relay it, its armature l9 returns to its central position, as shown, thereby breaking the circuit through the relay 53 and causing the opening of its upper and lower contacts 54, 55. Opening of the contact 55 breaks the circuit of the winding 45 of motor 44 and stops this motor. The opening of contact 54 discontinues the short-circuit of resistor 29 and thereby immediately restores the tone frequency of generator 23 to the transmission.

To obtain a uniform sensitivity or uniformity of control of the impulse motors 4'3 and 44 for equal adjustments of the control stick 2 and rheostat arm I3 throughout their range of control, the rheostat arm l and compensating resistor H are provided. With the control stick 2 in its neutral position, the rheostat arm I0 is disposed in its central position and the value of resistor H which is in series with the Wheatstone bridge circuit comprising the bridge arms 9 and i2 is substantially zero. As the control stick 2 is displaced from its neutral position in either direction, however, to unbalance the bridge circuit for the purpose above described, the movement of rheostat arm l0 along the resistor II, serves to add resistance in series with the bridge circuit, the amount of this added resistance being such as to secure the desired uniformity of action of the polarized relay l and the impulse motors 43, 44 for equal displacements of the control stick throughout any portion of its range of movement. The compensating resistor H is preferably designed so that the rate in the increase of its resistance, which is included in series with the bridge circuit, preferably increases as the control stick 2 is moved from its neutral position toward either of its extreme positions. This result may be secured by tapering the resistor ll so that its resistance per unit length increases steadily from its center toward its ends, or may be approximated by making it in sections, the. resistance of each section being uniform along its length, but the resistance of successive sections increasing from the center toward its ends. In the absence of a suitable compensating means, such as the resistor II, it has been found that the bridge circuit has a minimum sensitivity at the neutral position of the stick '2, and a maximum sensitivity of control at either extreme position thereof. This invention provides a means for securing a uniform sensitivity throughout the range of movement of the control stick. While the rheostat arm III is shown as mounted on the v shaft 2, it could be mounted on the motor shaft i8 instead.

To control the sensitivity level of the polarized relay 15 or, in other words, to control the proportion of the bridge current which passes through its winding i5 when the bridge is unbalanced, a variable resistor I4 is shown connected across the ends of winding l5. This resistor is varied by means of a rheostat arm 55 connected to a control shaft 51 having an operating knob 58. In order to provide for the change in resistance of the cross arm of the bridge circuit including the relay winding l5 which would otherwise occur upon the adjustment of the shunting resistor H, a second adjustable resistor l3a is provided and connected in series between one end of resistor 14 and the rheostat arm 13, the portion of resistor l3a which is included in circuit being controlled by a second rheostat arm 59 carried by the shaft 51, as shown. The arrangement is preferably such that as the resistance value of i4 is increased, that of lie is simultaneously decreased and vice versa, the resistors being designed so that the total impedance of the circuit forming the cross arm of the bridge remains substantially constant for all adjustments of the shaft 51.

If the movement of stick 2 to rotate the shaft 3 in one direction is arranged to tilt the elevators upward from their mid-position to raise the airplane, then its movement in the opposite direction will tilt them downward to depress the airplane. Movement of the stick 2 to rotate the shaft I in one direction may be arranged to lower the right aileron from its normal wing position and raise the left aileron to thereby bank the airplane on its left side. Movement of the stick 2 in the opposite direction will then cause the right aileron to be raised and the left aileron lowered to cause the banking of the airplane on its right side. It will be understood that a bridge circuit as heretofore described is provided at the control station for each airplane or other part to be controlled and that a pair of sources of signalling tone similar to 22 and 23 are associated with each bridge circuit and connected to the tone bus bars 22 through-a transformer and resistance network similar to that above described.

The arrangement described causes the extent of movement of stick 2 to determine the time in:

terval required for the bridge circuit to be rebalanced and this corresponds to the duration of the omission of transmission of one tone and, therefore, also to the time during which one tone is transmitted to effect the remote control. Since, as will be explained later, the response of the controlled part of the airplane depends on the length of time of omission of a tone frequency, it follows that for optimum results, the closest possible agreement in phase relationship between the control lever at the ground station and that on the airplane should be secured. However, during the normal running of an airplane, the control lever 2 is frequently passed through its neutral or mid-position, at which point synchronization of the control lever on the airplane and that at the ground station is reestablished in case there is not a close agreement in phase relationship between them.

For the purpose of establishing this synchronization, means is provided to eliminate the tone frequencies of both the generators 22 and 23 from asst/arr cam on serving to open and close a switch at,

cam 62 to open and close a switch (aid and cam Bl to open and close a pair of switches 65 and 65. W hen the stick 2 is brought into its neutral position, as indicated at N in Fig. l, the switches 65 and 86 are loath closed. Closure of switch to serves. to energize a relay ill by current rrom'hattery 8 through the circuit shown which includes battery 8, switch 65, lead 68, coil oi. relay and lead, t9 which connects to the positive terminal or liattery ii. Energization of relay [ll causes its switch contact it to close, thereby establishing a short circuit across resistor 2t and eliminating the tone of generator 23 from transmission. The closure of switch 86 serves to energize the remernlcer of the airplane to continue its motion in the same direction until it reaches its eiitreme rearward position and is again in. phase with control lever 2.

1 For the purpose of readily eliminating all the tones from the transmission, a bus bar switch M is provided, the closure of which serves to short-circuit the tone bus bars 32 and eliminate the tones of all the generators connected thereto from the transmission. This causes all the controlled members on the airplane to be auto" matically returned-to their mid or neutral positions in a manner to he later described.

The arrangement shown in Fig. 2 is a duplicate of certain portions of that shown in Fig. corresponding parts being indicated by similar reference numerals primed. Also the cam and lay ll by current from battery 8 through the circult shown including battery 8, switch at, lead l2, coil of relay ii, and return lead 89. Energization of the relay ll causes its switch contact l3 to close, thereby establishing a short circuit across resistor 26 and eliminating the tone of generator 22 from the transmission. The omission of the tone frequencies of both generators 22 and 23 from the transmission in the manner described causes the controlled shaft of the airplane, to be automatically moved into its neutral position by means to be later described.

While the control lever 2 is being moved forward in the direction the upper polarized relay contact it closes and causes the tone frequency 1 of generator 23 to be eliminated from the transmission in the mannerabove described. This causes the controlled member on the airplane to he moved in the same direction by means to he later described. Upon stopping the lever 2 in its extreme forward position, the cam 5% causes the closure of switch contact 68 which establishes the circuit shown including battery it, switch 63, lead 69 and the winding of relay El. @peration or this relay causes its contact it to close, thereby estalolishing a short-circuit across resistor 29 and the consequent elimination oi the tone frequency of generator 23. as long as lever 2 is held in its extreme forward position. This omission of the tone of generator 23 causes the controlled memlcer or the airplane to continue its motion in the same direction until it reaches its extreme for ward position when it is again in phase with control lever 22.

In a similar manner, movement of lever 22 rearwardly in the direction Rcauses the elimination of the tone of generator 22 from the transmission in the manner hereinbeiore described. This causes the controlled member on the airplane to he moved in the same direction by means to he later described. Upon stopping the lever 2 in its extreme rearward position, the cam 652 causes the closure oi switch contact 6d which establishes a circuit including battery 8,

contact 6 3, lead "112 and. the winding of relay ll.

Dperation or" this relay causes its'contact F8 to close, thereby establishing a short=clrcuit across resistor 26 and the consequent elimination of the tone frequency or generator 22 from the transmission while the lever 2 is maintained in its extreme rearward position. This omission of the tone of generator 22 causes the controlled through the circuit shown.

switch arrangement shown associated with shaft (1 is similar to that shown and described in connection with shaft 3 so that further detailed description thereof is unnecessary, similar parts being indicated by similar reference numerals primed. in this case, however, the generators 22' and 23 are arranged to generate frequencies of 1860 cycles and. 2460 cycles, re-

snectively, although it will be understood thatother suitable frequencies may he used instead. Movement of lever 2 about the longitudinal axis causes shaft 8 to rotate and rheostat arm 63' to unbalance the bridge circuit comprising resistors c' and i2. Movement of lever 2 to the left, as indicated at L, causes the operation of relay l5 and closure of its lower conltact it. This causes the energization of relay 31' by current from the battery 8' through the circuit shown. Operation of relay 3'5 causes its upper and lower contacts 38' and 39' to close, the closure or" contact 38' causing a short clrcuiting of resistor it through the circuit connections shown and the elimination of the tone of gen= orator 2'2 from the transmission, thus causing the aileron control shaft to he moved to the left. Upon moving lever 2 into its extreme leftward position, the cam 52' causes the closure of its switch contact which in turn causes the energization of relay ll by current from battery it through the circuit shown. Theclosure of contact 713 of this relay causes the short-circutting of resistor 26' and the continued elimination of the tone of generator 22' from the transmission as long as the lever 2 is maintained in its extreme leftward position. Should ior any reason the aileron control shaft not be in phase with the lever 2 when the latter reaches its extreme leftward position, it will "be automatically adjusted into such an in-phase relation icy means to be later described. Upon stopping the lever 2 in an intermediate position, the rheostat arm ll is automatically rotated by the motor 53' into such a position on resistor l2 as to balance the bridge circuit and again restore the tone of generator 22 to the transmission in the same manner as above described in connection with the generator 22 and motor 33.

Movement of the lever 2 to rotate the shaft 3 to the right, as indicated at it, causes the bridge circuit to become unbalanced in such a direction as to cause the operation of relay iii and closure of its upper contact lit. This causes the energiaation of relay 553' by current from battery 8' The operation. of relay 553' causes its contacts 5t and 55' to close, the closure or contact 5t causing a. short-circuiting of resistor and the elimination of the tone of generator 23 from the transmission.

This causes the aileron control shaft to be moved to the right during the period that the bridge remains unbalanced. The closing'of the lower relay contact 55 causes the operation of motor 44' and the re-balancing of the bridge circuit in the same manner as above described in connec tion with the motor 44. Upon moving lever 2 into its extreme position to the right, as indicated at r, the cam 80' causes the closure of its switch contact 83' which in turn causes the energization of relay 81' by current from the battery 8' through the circuit shown. The closure of contact 10 of this relay causes the shortcircuiting of resistor 29 and the continued elimination of the tone of generator 23' from the transmission as long as the lever 2 is maintained in its extreme position to the right. Means to be later described is provided on the controlled airplane to automatically adjust the aileron control shaft into its extreme position to the right in phase with the lever 2 should it, for any reason, not be in phase therewith. The cam GI and its cooperating contacts 85, 86' serves to cause the elimination of the tones of both the generators 22' and 23' from the transmission when the lever 2 is adjusted into its neutral position in the same manner as above described in connection with the corresponding cam SI and generators '22 and 23 of Fig. 1. The elimination of these tone frequencies from the transmission causes the controlled member on the airplane to be automatically restored to its neutral position in phase with the lever 2, should it not be in such neutral position, by means to be later described.

Referring now to Fig. 3, which shows schematically the apparatus mounted on the controlled airplane for controlling its elevators, a receiving antenna Ila is connected to the input terminals of a tunable radio receiver I5 which is provided with known means for receiving the carrier wave of transmitter 35 and detecting and amplifying its modulating frequencies. The output of receiver I5 is applied to the tone bus bars I8 to which a plurality of tunable amplifying channels E, Ea, E, Ea responsive to the tone frequencies of generators 22, 23, 22' and 23', respectively, are connected. Each of these channels is similar in construction and comprises a frequency selective network comprising an isolating resistor 11 and two parallel resonant circuits I8, 19, both tuned to the audio frequency to which the particular channel is responsive. The selected cur rent is amplified by the amplifier tube 80 and rectified by the rectifier tube 8I, the rectified output of tube 8| being amplified by the direct current amplifier tube 82. The plate circuit of amplifier tube 82 is arranged to actuate a relay 83- and comprises the resistors 84, 85 and a plate battery 86. One terminal of battery 88 is connected to an adjustable contact 81 which is preferably so adjusted that no direct current flows through the winding of relay 83 when the tone frequency to which channel E is responsive is not being received. The channel Ea is similar in all respects to channel E, except that its input circuits 18a, 19a are resonant to the frequency of generator 23, its output circuit being connected to relay 83a. Relay 83 is provided with a pair of armatures 88, 89 adapted to selectively engage the inner contact 9I and the outer contacts 92, 93. The corresponding contacts of relay 83a are designated 9Ia, 92a, 93a and its armatures 88a, 39a.

For each of the relays 83, 83a a self-vibrating motor .94, 94a is provided, these motors being similar manner by the relay 83a.

similar and each comprising a coil 95 and a movable armature 98 provided with a movable contact 91 and a pawl 98 which cooperates with the teeth of a ratchet wheel 99 mounted on a shaft I00. The movable contact 91 of motor armature 96 is connected, as shown, to armature 89a and current is supplied to coil 95 by a battery IOI. A spring I02 having one end connected to a stationary point and its other end to armature 96 serves to move pawl 98 to the right after the motor circuit is broken by movable contact 91.

When the relays 83, 83a are both energized clue to the transmission of the tone frequencies of both the channels E and Ea, the energizing circuits of motors 94 and 94a are open at contacts 92, 92a so that both motors are at rest. When, however, one of the relays, as, for example, relay 83 becomes de-energized, due to the cessation of transmission of the tone of channel E, its upper contact 92 is closed, thereby completing the circuit of motor 94a and causing its armature 96a torotate counter-clockwise and move pawl 98a a sufliclent distance to engage pawl 98a behind the next ratchet tooth. The motor circuit is simultaneously broken by movable contact 91a, whereupon spring I02a causes pawl 98a to advance the ratchet 99a one tooth in a counterclockwise direction. This motion of armature 96a causes contact 91a to again close the motor circuit through coil 95a and the motor thus continues to vibrate and advance the ratchet wheel 99a during the time that the tone of oscillator 22 is not being received. Suitable holding pawls I03, I03a cooperate with the ratchets 99, 99a to prevent their reverse rotation. Rotation .of ratchet Wheel 99a is transmitted by shaft I00a to the input of a differential gearing device I00 having the output or driven shaft I05. Shaft I05 controls the rotation of a driven shaft I06 through a torque converter or amplifier I01 which may be operated by suitable power means such as an electric motor M. A driven sprocket wheel I08 is secured to shaft I05 and in turn is connected to the elevators S by the connections shown including a sprocket chain I08a. The other input shaft I00 of differential I04 is controlled in a The torque converter I01 performs the function of increasing or amplifying the torque supplied by its input shaft I05 and causing its output shaft 106 to rotate in the same direction and through substantially the same angle as its input shaft I05. A suitable torque converter for this purpose is shown and described in the patent application of William A. Black, Ser. No. 284,644, filed July 15, 1989, Patent No. 2,248,942, dated July 15, 1941. This arrangement causes the desired adjustment of the airplane elevators and shaft I08, although the torque applied to shaft I05 by the impulse motors is of small value.

The arrangement described causes shaft I06 I and the elevators to remain stationary when the tone frequencies of both the generators 22 and 23 are being transmitted to the receiver I5 and this shaft to rotate in one direction or the other, depending upon which of the tones is omitted, and its rotation will continue for a period of time equal to-the duration of the omission. In the example illustrated, motion of lever 2 (Fig. 1) clockwise or forward in the direction of F causes the elimination of the tone frequency of generator 23, to which channel Ea is responsive, and the operation of motor 94 and rotation of elevator control shaft I06 to the right or clockwise. During the movement of lever 2 the tone frerhecstat it trig. i) has been I by motor to sittlcient distance along resistor i2 to again bale e Wheat-stone bridge cy oi generator is he actuation oi ruption of the so that both thereby breaking the circuit of motor 9 1 at con- M tact @205, which stops the motor; in this manner, exact correspondence in phase position of control lever 2 and elevator sprocket wheel i is assured in the extreme clockwise position and. the elevators are helcl in their extreme position.

Upon returning control lever 52 toward its neutral position, the bridge circuit is unbalanced in the opposite direction causing omission of the tone of generator 222 from transmission in the manner heretofore described. The tone of generator 23 energizes the channel lZ'a causing the operation of relay 83c and motor tile with the consequent rotation of sprocket wheel tilt to the left toward its neutral position. This rotation continues until the control lever 2 reaches its neutral position when the tone frequencies of both generators 22 and 28 are omitted from the transmission in the manner hereinbefore described. This omission causes both the relays 8t and. 88a to become ole-energized, as shown in Fig. 3, so that the circuits of both. the motors to and tie are interrupted and both the motors brought to a stop.

If the sprocket wheel too should not be in phase with control lever 2, as. for example, if it is lag glng behind lever 2 after the bridge circuit is again balanced by the automatic adjustment of rheostat arm ill (Fig, 1), both the relays lit and 83a (Fig, 3) are deenergized. The circuit shown including motor coil 95c, battery iili, contact 92, contact 93a and movable contact iii which cooperates with a cam H2 is closed, causing operation of the motor 94a and continued rotation of sprocketwheel M8 until it reaches neutral posi-. tion when the motor circuit is broken at contact I and operation of the motor S lo ceases. A similar cam H20; and movable contact llia serve in a. similar manner to secure operation of motor 94 and adjustment of sprocket wheel tilt into its neutral position from the opposite direction. Proper in-phase relationship between the elevator control sprocket wheel lit and the manual control lever 2 in their neutral positions also is thus assured.

A similar operatlontakes place in adjusting the sprocket wheel its and the elevators from their neutral to their extreme leftward positions. Movement of lever 22 counter-cloclswise or rearwardly in the direction of R (Fig. l) unbalances the bridge circuit and causes the elimination of the tone frequency oi generator 2? from the transmission this causes channel E i. 3 and relay to remain unenergizeol with the con quent operation oi motor O in in manner simi lar to that above described in connection with channel. and motor 9 1.. When sprocket wheel tilt reaches its extreme left position is in phase with control lever 22, which is now its e2:- treine rearward position, a cam iii; causes clo sure oi contact lit, which in turn causes the has" sage of current from battery it through. the; winding of relay and the interruption at con tact of the circuit including battery Mill and the coil Sills of motor The motor {its being interrupted. no further movement of sprocket wheel to the leit takes place, but it remains in phase with control lever 22, both. being in their extreme co inter-clockwise positions, with the eievatcrs eir extreme position.

Fig. shows diagrammatically the means for controlling the ailerons of the airplane and comnrlses the channels ill and Ea, which are con-- structed similarly to channels .E and En above olescribed, except that the resonant circuits of channel E are designed to pass the tone frequency of generator 22 while those oi channel H pass the tone frequency of generator 23 Through the relays and 83a, which are similar to relays and tile, motors tit and that, which are similar to motors 536i and @4103, a differential tilt, torque converter till and shaft iilii' an aileron sprocket wheel lit is operated, this wheel being connected to the ailerons T by a sprocket chain ti ts and the gearing shown. Shait lilo has mounted thereon the cams Mil, M2, Mia and, i053 which coopcrate with the movable switch. contacts tilt, iii, Mia and Hi l, respectively, in the same manner as the cams Mil, M2,. lite and lit cooperate with their respective switch contacts, as above described.

With the lever 2 in its neutral position, as indicated at N in Fig. l, neither of the tone frequencies of generators 22' nor 23' is transmitted, the relays t3 and 83a are unenergized, motors 9G and Ma are not operated and aileron sprocket wheel M5 and the ailerons remain locked in their mid-position. Upon movement of lever 22 to the left in the direction of L, the shaft i is rotated causing the rheostat arm it to unbalance the bridge circuit comprising the resistors ii and 02. This causes the operation of relay it in such a direction as to cause the transmission of the tone frequency of generator 23' only. This causes the energization of relay 8342' which in turn causes the operation of motor 94a and rotation of shafts m5 and H16 to the left. This operation is continued until the rheostat arm ll (Fig. 2) has been adjusted along the resistor i2 by the motor it into such a position as to again balance the bridge circuit. Thereupon the relay it is ole-energized and the tone frequency of generator 22' restored to the transmission, whereupon the motor 95a stops and the aileron sprocket wheel ll 5 remains locked in its adjusted position. Should lever 22 be adjusted into its extreme leftward position, the tone of generator 23' continues to be transmitted in the manner above described in connection with the operation of generator 23 and lever 2. Rotation of shaft Hill to the left, therefore, continues, if sprocket wheelilt should not be in phase with lever 2, until these two members are again in phase, whereupon cam lit causes the closure of movable contact MG and the stoppage of motor 96a in the manner above described in oonnec tion with motor 940. and switch contact I ll. The shaft I08 and aileron sprocket wheel H then remain locked in their extreme leftward position until the control lever 2 is again moved towards the right.

Upon movement of lever 2 to the right in the direction of r from its extreme left-hand position, the movement of rheostat arm' i3 along resistor 9 unbalance the bridge in such a direction as to cause the operation of relay l6 and the transmission ofthe tone of generator .2 only. This causes the energization of relay 83' which in turn causes the operation of motor 94' and rotation of shaft I06 to the right. This action continues until the bridge circuit is again balanced by the adjustment of rheostat arm I1 along the resistor l2 by the motor 44'. Upon the rebalancing of the bridge circuit, the relay i5 is deenergized and the tone of generator 23' is restored to the transmission with the consequent operation of relay 83a and the sto page of motor 94', the sprocket wheel H5 remaining locked in its adjusted position. Upon the adjustment of lever 2 to its neutral position, the tone frequencies of both generators 22 and 23' are omitted from the transmission so that both of the relay 83 and 83a are unenergized. If at this time the sprocket wheel H5 has not yet reached its neutral position, a circuit is established by the operation of cam H20. and switch contact Illa, which closes the circuit through the coil of motor 54. The continued operation of motor 94' rotates the sprocket wheel H5 to its neutral position, when the motor circuit is broken at the contact Illa and operation of motor 94' ceases, locking the sprocket wheel I IS in its neutral position in phase with control lever 2.

If lever-,2 is moved to the right toward r beyond its neutral position, the tone of generator.

23' continues to be omitted from the transmission, the tone frequency of generator 22' only being transmitted. This causes the energization of relay 83' and the operation of motor 84', causing the rotation of shaft I08 and sprocket wheel H5 to the right or clockwise until lever 2 is stopped and the bridge circuit rebalanced by the adjustment of rheostat arm 11' along resistor I2 (Fig. 2) by the motor 44'. Upon the bridge circuit being rebalanced, the'tone frequency of generator 23' is restored to the transmission so that both the relays 83' and 03a are energized and the circuit of'motor 04' broken in a. manner above explained in connection with the relays 83, "a and motor 84. Upon moving lever 2 further toward its extreme clockwise position, the operation of motor 94' is resumed, and if after the lever 2 reaches its extreme clockwise position and the bridge circuit has again been balanced by the adjustment of rheostat arm l'l along resistor [2, the sprocket wheel ll! (Fig. 4) has not yet reached its extreme position to the right, the transmission of the tone frequency of generator 22' continues, causing continued operation of motor '84. Upon the sprocket wheel H5 reaching its extreme right-hand position in phase with control lever 2, the cam H0 causes the closure of switch contact I09 and the stoppage of motor 94' in the manner above explained in connection with motor 94, cam H0 and contact I08 (Fig. 3).

It is thus seen that means is disclosed to provide in-phase relationship between the aileron sprocket wheel and the operators control lever in their neutral positions and also in both their extreme operating positions.

The torque amplifier motors M are shown in Figs. 3 and 4 as being supplied with current from a single current source illustrated as a storage battery H6 through a circuit including the leads H1 anda movable switch contact H8.

From the foregoing it will be readily understood that upon the closure of switch 14, Fig. 1, by the operator at the ground station and the consequent elimination of the tone frequencies of all the generators 22, 23, 22 and 23' from the transmission, both the controlled shafts I06 and Hill (Figs. 3 and 4) will be automatically returned to their mid or neutral position by means of the cams H2, Il2a, H2 and Illa. in the manner previously described. The switch 14, therefore, provides a very convenient means for permitting the operator to quickly restore the elevators and ailerons of the controlled plane to their normal or neutral position.

I have described what I believe to be the best embodiments of my invention. I do not wish, however, to be confined to the embodiments shown. but what I desire to cover by Letters Patent is set forth in the appended claims.

I claim: V

1. Means for adjusting an oscillatable device in either direction from a normally neutral position, comprising in combination, a normally balanced Wheatstone bridge, a compensating impedance, a manual control member adapted for unbalancing said bridge, means controlled by said manual control member for connecting a variable portion of said compensating impedance in series with said bridge in accordance with the extent of adjustment of the manual control member, automatic means for restoring the bridge to a, balanced condition, and means responsive to the unbalanced condition of the bridge for causing the movement of the device in a predetermined direction during the interval while the bridge remains unbalanced.

2. Means for controlling an adjustable device comprising, in combination, a Wheatstcne bridge comprising a pair of oppositely disposed resistors, a source of steady potential connected across the ends of said resistors, a circuit connected across a pair of points on said resistors whichare of substantially the same potential, said circuit comprising a current responsive device and a pair of contacts adjustable along said resistors and means for causing a substantially equal response of the current responsive device for equal movement of one of said adjustable contacts along its resistor throughout its range of movement, said means comprising a. device for regulating the' value of the current from the steady potential source passing through the Wheatstone bridge.

3. The combination as set forth in claim 2 in which an adjustable resistor is connected across the terminals of the current responsive device to control the sensitivity thereof.

4. Means for controlling an adjustable device comprising, in combination, a Wheatstone bridge comprising a pair of oppositely'disposed resistors, a, compensating resistor having its midpoint connected to one end of said bridge, a circuit connected to the other end of said bridge and comprising a source of steady potential and a first contact adjustable along said compensating resistor; a circuit adapted to be connected across the centers of said pair of resistors and comprising a current responsivedevice and a second contact which is adJuStable along one of the resistors of said pair; and a single control means arranged to adjust the second contact along its we 5. eel-um whim the silk, adjust ifl" e with. me seeemfl e e register;

' m sh e1? mid nee-1 ends 3S u :2 mid pm den,

'1. The eombinemen as set fie ellemu. 4; :"m which the eenmeeteel aerat me e0 menses a mm "eifle aims the resister e? the 1.1, @ummatie means fer adjusting the u" "d calms-mi; iae rebelanee the bridge.

fer eentmlllirg en wstebiie deviee comprising, in cem-bmetwn, Wheatsmne bridg cempming e pair 03 eppoeiu'eiy dispeeed re isters, 2, 80121436: of steady petentiefl eemaeefiee memes the ends (of said resistors, a circuit eexmeeteel eeross a, pair of points on said.- resisters which are of substantially the same putemiel, said eireufi; comprising a currents respamsive device and.- e pair ef eentecize edjusteble aleng said resistors, adjustable means for een'isremng the sensitivity 01 said current respemive device and meme for memteming the imzmedemee @f eflweuit lbe= The eembmatien e5 set forth in $3 which the edjus means eemprises VP Pele resist-m: eenmeeted. across the texmmem 0 cement respemsive device and the q. maintaining impedance @f the eimui'i; um stew-05s 1 eemfsenn'; eempmsee e verieble emmeetezi in "min-h iahe eumem resp'nnse device.

ML Means fer eemmlling an adjustable c' -qrgge eempzismg, in eembimefbion, Wheetstene 'fige having four eech arm having e seuzrce ef steady putential, a circuit connected, memes e pair e3 mints en said arms Whieh @Z eubstemtially the same potential, eimuit eemprismg a current respnnsive deviee and cement edjuszable alone was or? the bridge arms,

em energizing eireuit eonnecting said patent-1a seurce ice a pair 0f diagonal paints on the b1, arms, said energizing circuit including a wnneeted impedance and single centre], m

heir arranged to: adjust said. contact along its bridge arm to unbalance the bridge and t0 simultameously increase said lastqmmed impedance,

11., A. control means as set forth in claim M in which the series connected impedance eem= mi es & tapered resister.

DONAIEJ) memes; 

